The present invention relates to mixing apparatus, for mixing materials, such as aggregates used in the construction industry, and in particular to apparatus which not only mixes the materials, but then conveys the mixed material to the required point of discharge. Such apparatus is commonly known as mixer-placer apparatus. The invention also relates to a mixing vessel and to a suction conduit assembly for such apparatus.
Concrete floors, for example, may be laid and screed with mixer-placer apparatus. Although traditionally, this technology is used in the construction industry, the technology can be applied to other industries where mixing and displacement of materials is required.
Existing mixer-place machines comprise a diesel engine which drives an air compressor. The diesel-engined compressor is typically mounted upon a wheeled chassis, or road trailer, which also supports a cylindrical batch holding vessel. The holding vessel serves as a mixing vessel and thus includes a rotatable mixing paddle arrangement. The mixing paddle arrangement is powered either by a hydraulic pump and motor or a belt drive or gear box. The cylinder is mounted with its axis horizontal and the mixer paddle drive shaft is on the axis of the cylinder.
The holding/mixing vessel is provided with a large charging opening in the upper part of the cylindrical side wall, the opening being closable by a lid and seal arrangement, which provides an air-tight seal to the vessel on closure of lid. This allows the contents of the vessel to be pressurised.
A delivery hose is connected to an outlet provided in the lower side wall of one end of the mixing vessel, to deliver the mixed product to the required location once the mixing stage is completed. A pneumatic supply line from the compressor is connected to the mixing vessel to effect discharge of the mixture, once mixing of the constituents is completed. Therefore, the principal function of the compressor is to pressurise the mixing vessel for discharge.
In use, when the mixing apparatus is to be used for mixing a floor screed material, the mixing vessel must first be charged with the sand, cement and water, in the required proportions. The lid covering the charging opening is removed, and a measured quantity of sand is shovelled into the mixer vessel from an adjacent sand heap. A bag of cement is split and also emptied in, together with the required amount of water and any additives required. During this process, the paddles are rotated, and once loaded, the lid fastened down securely, whilst the mixing process is completed.
Once mixing is complete, compressed air is admitted to the mixing vessel via the air inlet. The paddles in the mixing vessel urge the material towards the discharge outlet. As the mixture covers the opening, the mixture discharges and is conveyed by the pneumatic pressure from the compressed air through the delivery hose. A hose tripod device may be employed to kill the energy in the concrete and allows it to fall in a heap beneath it whence it is spread and levelled.
It will be appreciated that the time spent filling the mixing vessel occupies a significant part of the cycle, and that this is a labour-intensive stage.
In addition, with current mixer-place machines, great care needs to be taken to clean the lid for the charging aperture, and its seal to ensure that the seal is effective. This step is time consuming, and adds to the overall cycle time for a batch of mixture. In addition, it has been found that the handling at this step can serve to accelerate the deterioration of the seal.
If the total cycle time could be reduced, and if the labourer's time could be better utilized, then the total operational efficiency of the process can be improved.